There has developed over the years, a class of blow molding machine known as the "inject, extrude and blow" machine, wherein the neck or finish of the container is injection molded in an injection mold superimposed on an annular orifice. After the mold is filled from the orifice, the mold is moved away from the orifice as a tube integral with the material filling the mold is extruded through the orifice. A blow mold is then closed on the tube between the neck mold and the orifice, pinching the tube shut near the orifice. Blow air is then injected through the neck mold into the tube, and the tube is simply inflated to the configuration of the blow mold. This type of machine is illustrated and described in detail in U.S. Pat. No. 3,008,192 to Allen et al.
In early attempts to adopt such injection, extrude and blow machines to the manufacture of handled jugs or the like, it was found impossible to extrude a tube having an integral injection finish and of sufficient diameter to provide material properly located in the parison to be pinched shut by the blow molds for forming an integral handle upon blowing. Attempts have been made to freely inflate or "puff" the tube to a diameter sufficient to provide an entrapped handle area but in the absence of precise control over the size of the tube, much "flash" or waste material was formed upon closing of the mold. Further, elaborate and expensive false finishes and funnels were injected, but again, excess flash was generated. Further, complicated and costly deflashing and finish facing machines were required, the amount of the scrap generated made the process economically unfeasible, and the severing of the scrap at the seams and edges of the bottles always generated the possibility of leakage in the final container. Finally, and most importantly, all of the advantages of a precisely formed, exactly dimensioned injection molded finish were lost by the various expedients which were developed in the art.
Additionally, it has been found that it is practically impossible to obtain the advantages of biaxial orientation in thermoplastic materials by attempting to inflate a relatively small diameter tube in one single blowing operation to a relatively large container, such as a handled jub. The material distribution inherent in the movement of the plastic material during blowing is such that all parts of the container would not be equally oriented, nor would the wall thicknesses throughout the container be uniform.
Thus, the prior systems, in addition to the practical difficulties outlined above, also suffer from the fact that the maximum potential of the thermoplastic material cannot be realized, because of the effective impossibility of biaxial orientation during forming of the container.